1. Field of the Invention
The invention relates to a device for monitoring the dimensional, shape, and positional tolerances of a mechanical workpiece. The device comprises at least one measuring probe each having a housing, attached to a support, with two separate inductive coils and a sensing stylus resting on the surface to be measured of the workpiece and made of a non-magnetizable material. The stylus is embodied as a piston and supports a deflector body that is in the form of a sleeve, wherein the stylus together with the deflector body is movable by a force into its measuring position.
2. Description of the Related Art
Such a measuring probe is disclosed in German published patent application 195 12 836. In a housing of the measuring probe that is covered by a plate serving as a seal and a guide for the sleeve, a measuring inductive coil and a compensating inductive coil with outwardly extending connecting cables are positioned adjacent to one another for forming a so-called half-bridge; they are embedded in two coil supports comprised of magnetizable material. A coil core sleeve acting as a deflector body is arranged on the sensing stylus and projects in its initial position only minimally into the measuring inductive coil. With increasing measuring travel, the immersion depth of the coil core sleeve in the measuring inductive coil increases. Even though the immersion depth of the deflector body correlated with the compensating measuring coil is manually adjustable, it remains unaffected by the measuring travel and thus the stroke of the sensing stylus. A chamber arranged below the plate covering the housing and delimited by the measuring probe and the support can be loaded by a pressure medium that causes the sensing stylus to contact the workpiece. The travel that is performed when doing so corresponds to the measuring travel that can be detected by the resulting resistance change between the inductive coils connected in series.
Since for such a measuring probe only the impedance of the measuring inductive coil changes as a function of the measuring travel, the total resistance changes by the same amount and thus also the current consumption so that the measuring signal does not behave approximately proportional to the measuring travel and the required measuring amplifier is loaded extremely differently. As a result of the currents of different magnitude, the measuring probe is also differently loaded thermally so that with such a measuring probe, even at high electrical expenditure for linearization of the measuring values, no useful measuring results can be obtained.